Get it Growing: Your crape myrtle questions answered

V. Todd Miller, Kirk-Ballard, Heather

(7/23/2021) There’s a lot going on with crape myrtles this summer. I’ve gotten quite a few calls about these highly prized ornamental trees of the South.

With all of the rain that we have had over the past month, we have already surpassed our annual average rainfall and we are only halfway through the year. Since January, we have received around 63 inches of rain. That’s keeping lawns saturated and making it difficult to get any garden work done, much less mowing lawns.

With the rain, many plants have been able to grow. Others are beginning to suffer. Crape myrtles seem to be doing both in some cases. There is a lot going on with crape myrtles this summer. I have gotten quite a few questions about these highly prized ornamental trees of the South.

You may have noticed that crape myrtles are losing their bark. This process is very natural for crape myrtles and is one of the reasons why they are so beautiful in the winter. This feature is called exfoliating bark.

Crape myrtles lose their bark in the summertime to reveal smooth inner bark. It is one of the most beautiful characteristics of the plant. Colors range from light tan to gray to cinnamon or rust depending on the cultivar giving the bark a paint by number appearance.

Crape myrtles traditionally shed on an every-other-year schedule. However, they can have heavier years like the one we are experiencing this year due to exponential growth. Think of it like a snake shedding its skin as it grows – similar concept. As the trunk expands from growth, they shed their bark to allow the trunk to enlarge. With good rains and sunshine, these trees are growing.

Another issue I am getting questions about is why trees are dropping their leaves. This also can be in response to all of the heavy rains. Waterlogged areas can cause stress to trees, which then drop leaves in response to that stress. Once the soil dries out, if the roots did not suffer significant damage from water, the tree will leaf out again.

Leaf spot is another cause of the observed leaf drop. Leaf spot can be caused either a bacterial or a fungal pathogen. Again, trees drop their leaves in response to the stress. Rake leaves up and discard of them in the trash to prevent any further spread. Trees will leaf out again as moisture levels and pathogens decrease. It is not recommended to apply any chemicals.

Lastly, you may have noticed silver webbing or a cluster of tiny brown-gray insects on the bark of your crape myrtles. These insects are soft-bodied with tiny wings and antennae and are not related to the icky lice you might be familiar with. These small insects may be alarming at first sight, but they do not cause harm to the trees. They typically feed on algae, fungi, mold and the exfoliating bark.

Bark lice typically clean house after they are all done and consume their webbing at the end of the season. Therefore, we consider these little critters to be beneficial scavengers cleaning up the area. Perhaps add a tasty treat for birds in the area as well.

Another issue with crape myrtles is bark scale, which has become a real problem here in the Gulf South. Crape myrtle bark scale is an introduced insect pest from Asia, and it has a great affinity for crape myrtle trees. The problem usually goes unnoticed until plants begin turning black with a fungus called sooty mold when it begins to grow on insect droppings.

The insect has spread from the early 2000s throughout the South, affecting more and more trees. The management practices sometimes call for chemicals that can be harmful to the environment and ecosystems if not used properly.

Catch crape myrtle bark scale early. Treat with organic options such as neem or year-round horticultural oil. You will likely need to apply more than once after seven to 14 days to get newly hatched eggs. In addition, you can use a mild, room temperature, soapy water and soft scrubbing brush to remove the scale and black sooty mold. Heavy infestations may involve using chemicals labeled for use on scales, but these chemicals also will be harmful to pollinators.

Bark lice.

Bark lice are not harmful. They help clean up the exfoliating bark on crape myrtles. Photo by Heather Kirk-Ballard LSU AgCenter

Exfoliating bark on crape myrtles.

Exfoliating bark on crape myrtles is one of the great focal points of this plant. Photo by Heather Kirk-Ballard LSU AgCenter

Leaf spot.

Leaf spot causes crape myrtles to drop leaves. Trees will recover. Pick up and dispose of leaves. Photo by Heather Kirk-Ballard LSU AgCenter

Leaf Spot.

Leaf Spot on crape myrtles. Photo by Heather Kirk-Ballard LSU AgCenter

 Bark exfoliation.

This year has been exceptional for bark exfoliation on crape myrtles. Photo by Heather Kirk-Ballard LSU AgCenter

7/23/2021 2:45:07 PM
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